/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.runtime.checkpoint;

import java.io.Serializable;

/**
 * Helper for keeping track of min/max/average summaries.
 */
public class MinMaxAvgStats implements Serializable {

	private static final long serialVersionUID = 1769601903483446707L;

	/** Current min value. */
	private long min;

	/** Current max value. */
	private long max;

	/** Sum of all added values. */
	private long sum;

	/** Count of added values. */
	private long count;

	MinMaxAvgStats() {
	}

	private MinMaxAvgStats(long min, long max, long sum, long count) {
		this.min = min;
		this.max = max;
		this.sum = sum;
		this.count = count;
	}

	/**
	 * Adds the value to the stats if it is >= 0.
	 *
	 * @param value Value to add for min/max/avg stats..
	 */
	void add(long value) {
		if (value >= 0) {
			if (count > 0) {
				min =  Math.min(min, value);
				max = Math.max(max, value);
			} else {
				min = value;
				max = value;
			}

			count++;
			sum += value;
		}
	}

	/**
	 * Returns a snapshot of the current state.
	 *
	 * @return A snapshot of the current state.
	 */
	MinMaxAvgStats createSnapshot() {
		return new MinMaxAvgStats(min, max, sum, count);
	}

	/**
	 * Returns the minimum seen value.
	 *
	 * @return The current minimum value.
	 */
	public long getMinimum() {
		return min;
	}

	/**
	 * Returns the maximum seen value.
	 *
	 * @return The current maximum value.
	 */
	public long getMaximum() {
		return max;
	}

	/**
	 * Returns the sum of all seen values.
	 *
	 * @return Sum of all values.
	 */
	public long getSum() {
		return sum;
	}

	/**
	 * Returns the count of all seen values.
	 *
	 * @return Count of all values.
	 */
	public long getCount() {
		return count;
	}

	/**
	 * Calculates the average over all seen values.
	 *
	 * @return Average over all seen values.
	 */
	public long getAverage() {
		if (count == 0) {
			return 0;
		} else {
			return sum / count;
		}
	}

}
